Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.30	4.436%	$169.4996	$169.50	$169.50	$169.50
Purchase #2	$38.76	10.605%	$42.8705	$42.87	$42.85	$42.90
Purchase #3	$113.85	12.409%	$127.9776	$127.98	$128.00	$128.00
Purchase #4	$168.39	10.521%	$186.1063	$186.11	$186.10	$186.10
Purchase #5	$56.74	7.748%	$61.1362	$61.14	$61.15	$61.10
Purchase #6	$207.47	5.820%	$219.5448	$219.54	$219.55	$219.50
Purchase #7	$244.50	12.252%	$274.4561	$274.46	$274.45	$274.50
7 purchase totals =	$992.01		$1,081.5911	$1,081.60	$1,081.60	$1,081.60